In the production of optoelectronic components, for example LEDs or semiconductor lasers, it is often desirable for a growth substrate used for the epitaxial growth of a semiconductor layer sequence of the optoelectronic component to be subsequently separated from the semiconductor wafer.
By way of example, in so-called thin-film technology, firstly the semiconductor layer sequence of an optoelectronic component is grown epitaxially on a growth substrate, afterward a carrier is applied to the surface of the semiconductor layer sequence opposite to the growth substrate, and the growth substrate is subsequently separated. This method has the advantage, on the one hand, that a comparatively thin epitaxial layer sequence remains on the new carrier, from which layer sequence the radiation emitted by the optoelectronic component can be coupled out with high efficiency, particularly if a reflective or reflection-increasing layer is provided between the epitaxial layer sequence and the new carrier. Furthermore, the growth substrate can advantageously be reused after it has been stripped away. This is advantageous particularly when the growth substrate is composed of a comparatively high-priced material, in particular sapphire, SiC or GaN.
When a transparent growth substrate composed of sapphire is used, the growth substrate can be stripped away from the epitaxial layer sequence for example by means of a laser lift-off method known from WO 98/14986 (corresponding to U.S. Pat. No. 6,559,075). However, said method cannot readily be applied to substrates composed of a nitride compound semiconductor, in particular GaN.
The document U.S. Pat. No. 6,815,309 discloses transferring a thin layer of a high-priced substrate, for example GaN, to a lower-priced carrier substrate.
The document U.S. Pat. No. 5,374,564 discloses a method for separating a thin semiconductor layer from a substrate, which is based on the implantation of hydrogen ions through the layer to be stripped away and a subsequent thermal treatment for producing blisters in the ion-implanted region, which brings about a thermal ejection of the semiconductor layer to be stripped away.
When said method is applied to a semiconductor wafer onto which a functional semiconductor layer sequence has already been deposited epitaxially, there is the risk of the quality of the functional semiconductor layer sequence being impaired during the ion implantation.
The document C. H. Yun, N. W. Cheung: Thermal and Mechanical Separation of Silicon Layers from Hydrogen Pattern-Implanted Wafers, Journ. of Electronic Materials, vol. 30, No. 8, 2001, pp. 960-964, discloses a method for the thermal or mechanical separation of a silicon layer from a silicon wafer.